MySql.Data.MySqlClient.ISSchemaProvider.GetForeignKeys C# (CSharp) Method

        public override DataTable GetForeignKeys(string[] restrictions)
        {
            if (!connection.driver.Version.isAtLeast(5, 1, 16))
                return base.GetForeignKeys(restrictions);

            string sql = @"SELECT rc.constraint_catalog, rc.constraint_schema,
                rc.constraint_name, kcu.table_catalog, kcu.table_schema, rc.table_name,
                rc.match_option, rc.update_rule, rc.delete_rule, 
                NULL as referenced_table_catalog,
                kcu.referenced_table_schema, rc.referenced_table_name 
                FROM INFORMATION_SCHEMA.REFERENTIAL_CONSTRAINTS rc
                LEFT JOIN INFORMATION_SCHEMA.KEY_COLUMN_USAGE kcu ON 
                kcu.constraint_catalog <=> rc.constraint_catalog AND
                kcu.constraint_schema <=> rc.constraint_schema AND 
                kcu.constraint_name <=> rc.constraint_name AND
                kcu.ORDINAL_POSITION=1 WHERE 1=1";

            StringBuilder where =new StringBuilder();
            if (restrictions.Length >= 2 && !String.IsNullOrEmpty(restrictions[1]))
                where.AppendFormat(CultureInfo.InvariantCulture, 
                    " AND rc.constraint_schema LIKE '{0}'", restrictions[1]);
            if (restrictions.Length >= 3 && !String.IsNullOrEmpty(restrictions[2]))
                where.AppendFormat(CultureInfo.InvariantCulture, 
                    " AND rc.table_name LIKE '{0}'", restrictions[2]);
            if (restrictions.Length >= 4 && !String.IsNullOrEmpty(restrictions[3]))
                where.AppendFormat(CultureInfo.InvariantCulture, 
                    " AND rc.constraint_name LIKE '{0}'", restrictions[2]);

            sql += where.ToString();

            return GetTable(sql);
        }